The burning of petroleum-based fuels, such as liquid diesel fuel, is known to contribute to poor air quality. As a result, efforts have been undertaken to develop engines, and their associated machines, that can operate using alternative fuels. Such alternative fuels, which may burn cleaner than petroleum-based fuels, may include, for example, natural gas, propane, methanol, ethanol, hydrogen, and biodiesel. Some development efforts have focused on providing cost-effective and reliable alternatives to petroleum-based fuels, while also utilizing the performance and efficiency advantages of compression ignition engines. Thus, one such alternative strategy includes configuring a compression ignition engine to operate using both liquid diesel fuel and natural gas fuel. For example, small amounts of liquid diesel fuel may be used to compression ignite the combined liquid diesel fuel and natural gas fuel.
For embodiments incorporating a diesel fuel injection valve and a natural gas fuel injection valve into a single fuel injector, it may be desirable to reduce pressure differentials between the two high-pressure fuels. It may further be desirable to maintain the liquid diesel fuel at pressures just above the natural gas fuel pressure to reduce leakage of the natural gas fuel into the liquid diesel fuel passages. Such leakage may result in damage to components of the fuel injector, such as the injection valves. Some conventional systems incorporate pressure relief valves for venting excess natural gas fuel, when necessary, to maintain a desired pressure differential. However, since natural gas fuel is primarily methane, venting the natural gas fuel to atmosphere is considered very undesirable, as methane is known as an extremely powerful greenhouse gas.
U.S. Pat. No. 7,627,416 to Batenburg et al. teaches an exemplary dual fuel internal combustion engine. In particular, the Batenburg et al. reference teaches a strategy for transitioning the dual fuel internal combustion engine from a dual fuel operating mode, in which both natural gas and diesel fuels are utilized, and a secondary fuel operating mode, in which only the natural gas fuel is utilized. The strategy includes switching between operating modes based on a pressure of the natural gas fuel at the injection valve. Although the Batenburg et al. reference is directed to an operating mode control strategy, the disclosure discusses the use of pressure control valves to maintain the desired pressure differential between the two fuel systems. As such, the Batenburg et al. reference suggests the undesirable venting of natural gas fuel mentioned above.
The present disclosure is directed to one or more of the problems or issues set forth above.